I think any remastering or restoration that is done as a commercial project even if it is on a public domain still gets a copyright of that specific copy. It does not include the original non remastered work.

YouTube's algorithms aren't really used to detect differences between remasters and originals. Especially so if the works contain the same frame-for-frame images/audio.

This is because many people have posted frame-modified illegal copyrighted films (adding border animations, watermarks or filters, etc) to get around exact-copy filters. You can thank piracy for that.

It would have a hard time telling the difference between a rip from a copyrighted remaster and the original which isn't copyrighted but looks almost identical (as far as DB is concerned).

A way around that could be is to appeal with your specific copy you have (granted that you know isn't currently in copyright anywhere) and get an appeal approved.

I wouldn't hold your breath as such appeals rarely get granted to individuals (at least not in a timely manner which most people want or need).

You might possibly have better luck with it if you were a commercial industry, and had a department dedicated to this sort of thing.

As time goes by this will get better, MLA is a learning technology in its infancy after all. That said, someone will have to "teach" it to do this. That might be a while, if ever.

This and other movies have false copyright claims on YouTube. Is there any way to fight these without disclosing my private information? Why is YouTube so very annoying? I love this movie. I wanted to watch it with my friends on my channel but nooooo

I'm surprised that any of the Castle films are public domain. This version of the film is the best print in the archive.